Metal coated ferrous article and process of making it



f Dec. 3, 1935.

F. M. cRAPo METAL COATED FERROUS ARTICLE AND PROCESS OF MAKING IToriginal Filed Aug. 12, 1931 i, M WNMMQLPOBM m M M @N l5@ or W I@LOUQLxfQL W ,WW/ 5 1A NN N\ $1 Nm: NN 08N ,1N New. A NN N v w 1 1 I I11 q. 1|.|.. 1 11H w .wwuwmu J 1 MMWMH 1:--

. 1|l S3 s is@ .fl ism 5am, Sum, 51@ awww ,5.85 @@Mwsm @ESSE .\Q\\ BSN53: @En susan 1&9@ AW LSuSm l sstnnsh" mfmr Patented Dec. 3, 1935 UNITEDs'labrlsv METAL COATED FEBROUS ARTICLE AND PROCESS F MAKING IT FrederickM. Crapo, Muncie, Ind., 'asslgno'r to Indiana Steel & Wire Company,Muncie, Ind., a corporation of Indiana original application August i2,1931, serial No.

Divided and'A this application August 17, i934, serial No. 740,231

s claims. (Ci. sin-68.2)

It is the object of my invention to produce on ferrous articles, andespecially on ferrous wire,

an improved metallic coating of which the Vpart next to the ferrousmetal is a zinc coating applied by the hot-galvanzing process, and ofwhich the outer part is substantially pure cadf Morelspecifically, it ismy object to make possible a heavy coating, in-which-the outer surfaceis of a very pure cadmium while'the inner part is of zinc iirmlyassociated with theferrous base by inter-"alloying This presentapplication is a division of my co-pending application Serial No.556,631, filed August 12, 1931, which resulted in Patent No. 1,984,335,granted December 11, 1934.

In carrying out my invention, I apply the coating in two parts. 'I'hefirst part is a zinc-coating, applied by the hot-galvanizing process,whereiny there is a certain inter-alloying between the zinc firmlyjoined to the article byits adhesion to the surface produced by thelhot-galvanizing. As a result I am able to get a heavy coating, ofwhichthe inner part of zinc is alloyed rmly withthe ferrous base, whilethe outer part is of comparatively pure cadmium. This composite coatingis of great advantage, because of thef high resistance whichrk thecadmium exterior offer-sto corrosion, especially to those types ofcorrosion of which a salt atmosphere is typical, while the under coatofzinc not only adheres well to the ferrous base and is relativelyinexpensive but in addition lfurnishes an excellent base for theelectroplated cadmium of the outer coat.

In carrying .out my invention, whether on fer- 'tous wire'v or otherferrous articles, the coating processes may be either continuous or bybatches; but I prefer the continuous process, especially for wire. f

The accompanying drawing 'illustrates nLv invention. In such drawing,Fig. 1 is an enlarged perspective view of a wire coatedin accordancewith my invention, with the coatings much magnifled in thickness, andwithout any attempt to' indicate any inter-alloying; and Fig. 2 is adiagram showing a continuous process forcoating `ferrous wire inaccordance with my invention;

I will describe my invention infconnectionhwitli,

theI continuous process indicated in Fig. 2,

although it is not limited tof-a continuous process'.

The wire to be coated may be a ferrous wire of any character, preparedfor coating in' any desired manner. I have not shown the wire- 5 drawingapparatus, since it is well understood; and r so indicate the wire Il!as coming from a pay-out reel I I. From that pay-out reel the wire I0may pass through an annealing furnace I2, Y V and then through cleaningand/or uxing baths 1o I3 and I4, for preparative purposes. Thesepreparatory treatments are conventional, and may be varied as desired.After 'the preparatory treatments, the wire Ill is passed through albathI5 of molten zinc; in which passage molten zinc 15 adheres tol andalloys with the surface of, the wire to provide the usualhot-galvanizing. If desired, although it is noty necessary, thezinccoated wire after it yemerges from the bath I5 of molten zinc maypass through a wipe I6. Also, although it is not essential to myinvention, the zinc-coated wire may now receive a heat treatment ifdesired, as by being passed through a heat-treating furnace 30. f A

Up to this point, the wire produced is hotgalvanized wire, and'may be ofany type. Y The hot-galvanized coating thereon forms the` first part ofthe coating of my present invention.'

The hot-galvanized wire is now treated to apply the second part of myvcoating thereto. This treatment may be made immediately after the wirehas been hot-galvanized, in the same continuous process; or it may beapplied at somelater time, although I deem that less desirable.

In the arrangement shown in Fig. 2, the second half of the coating isapplied in the same continuous process. The hot-galvanized wire Il,after/leaving the bath I5 of molten zinc, and the 'wipe Ii and/orheat-treating furnace 3l if they are used, is desirably passed through acleaning 40 bath I'I, of any suitable character, to prepare the wire forthe subsequent coating. The wire I! y then passes to the 'second coatingapparatus, for

which-I prefer an electro-plating bath IIA. In this bath the moving wireis the cathode, being connected to the negative side of a suitableelectric supply-circuit IS, as by trolleys 2l. The plating bathl alsohas a suitable anode 2l connected v f to the positive side of the suly-circuit. I have indicated this electro-plating th, as well as the 50other baths shown, merely tically; as

they may take any suitable form. From the electro-platingbath, the nowdouble-coated wire may l pass, through an intervening washing bath 22and over or through a drier 23 desired, to a take- 55 up reel 2l; bywhich take-up reel the power is applied for moving the wire.

The electro-plating bath I8 contains an electrolyte suitable for platingcadmium on to the already hot-galvanized wire; and the anode 2l is ofsuitable material for such cadmium plating. In

consequence, the second part of the coating is a coating ofcomparatively pure cadmium. As already stated, the hot-galvanizedferrous wire furnishes a good base for this electro-deposition ofcadmium. This second part of the coating may be as heavy as desired, sothat the total may be a heavy coating when and if desired; and the outersurface of thiscoating is of substantially` pure cadmium The nature ofthe electrolyte in the electroplating bath I8 may vary in accordancewith the known processes for cadmium plating; and so may the currentdensity used for. plating. My invention is not limited to any specificcharacter of electro-deposition, or to any specic electrolyte or currentdensity so long as they are suitable for electro-plating cadmium; but isintended to include not only electro-deposition of cadmium followinghot-galvanizing with zinc, but also to include other types of cadmiumcoating than hotdipping, applied at a temperature below the meltingpoint of cadmium to a wire or other ferrous article-which has beenhot-galvanized. l

The general nature of the resultant article, such as wire, is indicatedin Fig. 1. The ferrous core 25 is the initial ferrous wire, to which agalf vanized coating 26 of zinc is applied by any available hot-dippingprocess of galvanizing; and over the zinc coating 26 is-an outer cadmiumcoating 21 applied at a temperature below the melting point of cadmiumby a process other than hot- 1. A coated ferrous article, comprising aferrous base'having a hot-galvanized coating of zincA thereon, and overthat an electro-deposited coating substantially wholly of cadmium. l

2. A coated ferrous wire, comprising aferrous base-wire having ahot-galvanized coating of zinc thereon, and over that anelectro-deposited coating substantially wholly of cadmium.

3. The process of coating a ferrous article, l which consists inapplying toit a zinc coating by the hot-galvanizing process, andapplying to the hot-galvanized ferrous article by electro-deposition acoating substantially wholly of cadmium."

4. The process of coating a ferrous wire, which consists in passing itsuccessively through a bath of molten zinc and through anelectro-plating bath containing a suitable electrolyte for depositing acoating substantially wholly of cadmium.

5. A ferrous-coatedarticle as set forth in claim V1, in which thehot-galvanized coating of zinc is forth in claim 4, inwhichrthe firstcoating is i wiped before the second is applied.

FREDERICK M.- CRAPO.

